Engine and transmission manufacturers continue to seek ways to improve fuel economy and vehicle performance in powered vehicle systems. Conventional vehicle transmissions include software or a control scheme for determining when the automatic transmission shifts from one gear range (or ratio) to another gear range. This control scheme is commonly referred to as a “shift schedule” and is based on multiple factors, e.g., engine torque, vehicle speed, accelerator pedal position (i.e., throttle percentage), transmission output speed, and tractive effort. Any given shift schedule for a vehicle balances fuel economy against performance.
In addition, engine and transmission manufacturers work together to form an integrated system that drives vehicle performance. For instance, an engine may produce different torque levels to drive a transmission based on a specific driving condition. At a lower torque level, the vehicle may operate with better fuel efficiency but with reduced performance. At a higher torque level, the vehicle may perform better but consumes more fuel.
Many conventional vehicle setups control engine torque by monitoring a vehicle's acceleration. The reason for doing so is because there is no easy or convenient way to limit torque based on transmission performance. Most conventional transmission assemblies include a single centerline on which input and output shafts are disposed. The input and output shafts rotate at high speeds and accelerate/decelerate quickly such that it is difficult to control engine performance based on these speeds. Thus, engine torque is controlled by vehicle performance rather than transmission performance. However, integrating the engine and transmission such that engine performance is controlled based on transmission performance is desirable since the two assemblies are integrated with one another for different vehicle setups.
Therefore, a need exists for optimizing vehicle performance by controlling engine torque based on a transmission characteristic.